It is known that the grip performance of a pneumatic tire is greatly affected by tire temperature, and sufficient grip performance is not achieved in the low-temperature state. In particular, for racing tires for running on circuits, a rubber composition configuring tread is required to have exceptionally good dry grip performance. Therefore, a large quantity of carbon black fine particles or styrene-butadiene rubber with high glass transition temperature is blended into a rubber composition for use in tire treads. However, modulus and rubber strength of rubber compositions above will easily decrease in the high-temperature state. For this reason, when high-speed running continue for a long duration, wear resistance decrease, the state of wear of the tread surface negatively affected, dry grip performance gradually decrease due to heat sag, and, depending on the case, a blowout occurs.
Japanese Unexamined Patent Application Publication No. 2008-169295A proposes improvements of both tire initial grip performance and running stability by blending homopolymer resin and/or copolymer resin of an aromatic vinyl compound with the softening point of not lower than 140° C. to a tire rubber composition. However, performance requirements for a racing tire by users are becoming higher and there is a need for a tire rubber composition that can improve dry grip performance to or beyond conventional levels while retaining grip performance sustainability and wear resistance.